1. Field of the Invention
The invention relates to a flame retardant, curing adhesive film which is used to produce materials for aircraft interiors.
2. Description of the Prior Art
Materials used for interiors of commercial aircraft have typically been produced by embossing a curing adhesive film with a polyvinylflouride film, such as that sold under the trademark Tedlar by E. I. DuPont de Nemours & Company, Wilmington, Del. The purpose of the the curing adhesive film is to preserve the texture imparted to the Tedlar by the embossing or thermoforming operation and to provide flame retardant properties.
Flame retardant properties are quite important for material used in the interior of commercial aircraft and for some time the Federal Aviation Administration (FAA) has required that such materials pass a vertical burn test. Recently, in an attempt to improve the flammability standards for materials used in the interiors of commercial aircraft, the FAA has established a new test method which measures heat release rate from materials exposed to radiant heat. Details of the new test method are found in the Federal Register, Vol. 51, No. 139, Monday, July 21, 1986, pp. 26206-221. Generally, the method uses the heat release apparatus developed at the Ohio State University (OSU) and standardized by the American Society of Testing Materials (ASTM), ASTM-E-906. The apparatus measures the total heat release of the material tested in kilowatt minutes per square meter over the first two minutes, and also peak heat release in kilowatts per square meter. Under the new FAA standards, materials used in commercial aircraft cabin interiors must exhibit a total heat release over the first two minutes of less than 65 kilowatt minutes per square meter and a peak heat release of less then 65 kilowatts per square meter.
Prior art curing adhesive films which possessed suitable embossing retention characteristics and which passed the vertical burn test contained an organic binder component and approximately 40 to 80 weight percent of a fire retardant agent. The organic binder component of the prior art films included a hydroxyl terminated thermoplastic polyurethane elastomer, a phenoxy resin and a blocked aliphatic isocyanate prepolymer. The fire retardant agent of the prior art films included aluminum oxide trihydrate and antimony trioxide at a ratio of approximately 2.5:1.
When formed into a film at a typical thickness of 0.003" mils, these prior art films pass the vertical burn test. They do not, however, exhibit adequate heat release properties as measured by the new OSU heat release test.
It is an object of the present invention to provide a curing adhesive film which possesses the requisite flexibility and embossing retention characteristics and which possess excellent heat release properties by having a total heat release rate significantly less than 65 kilowatt minutes per square meter and a peak heat release rate of significantly less than 65 kilowatts per square meter.